Process for the production of high viscosity index lubricating oils



United States Patent US. Cl. 208-59 5 Claims ABSTRACT OF THE DISCLOSUREA process for the production of a wide range of high viscosity indexlubricating oils by hydrocracking a first feed, separating a light oilfraction from the hydrocrackate, hydrocracking a second feed and thelight oil fraction together, and recovering high viscosity indexlubricating oils, including a 100-150 neutral oil with a viscosity indexof at least 100 and an 800+ neutral oil with a viscosity index of atleast 95. The second feed is no heavier than the first feed, andpreferably is lighter. Reaction conditions and oil out points arespecified. Stabilization and dewaxing may follow the two hydrocrackingsteps.

BACKGROUND OF THE INVENTION This invention relates to the production oflubricating oils. More particularly, it relates to the production ofhigh viscosity index oils by hydrocracking.

Viscosity index (VI) is a measure of an oils rate of of change ofviscosity with temperature. A higher viscosity index indicates that theoils viscosity change is small over a wide range of temperatures. Thus ahigh VI oil is one that does not thin out at high temperatures norbecome viscous at low temperatures. Because of this property, high VIoils are considered premium oils. The best light oils are those with VIsof at least 100; and the best heavy oils are those with VIs of at least95.

Many lubricating oils as produced do not have particularly high VIs.Consequently, a number of processes have been proposed in the art forincreasing the VI of oils. These have included processes in which highVI components are added to a low VI oil or in which a low VI oil ishydroprocessed to raise the VI. Solvent extraction has also been used toimprove VI; the low VI components are extracted from the oil leavingonly the high VI components. It is apparent that each of these processeshas some disadvantageous features; either foreign materials must beadded to the oil or some oil yield is lost through extraction, oradditional processing steps are required.

In recent years, hydroprocessing has been actively investigated as ameans for producing lubricating oils with high VIs. These investigationshave centered around two basic types of hydroprocesses, hydrocrackingand hydrogenation. In general, hydrogenation has been used as afinishing step in lubricating oil manufacture. The raw oils, eitherstraight-run or produced by solvent extraction or some similar type ofseparation process, are hydrogenated at relatively mild conditions. Atypical such process is disclosed in US. Patent 2,967,144, in whichoxidation stability of an oil is improved by hydrogenation.Hydrocracking, which has been considerably less prominent in thelubricating oil area, has been used primarily to produce certain typesof lubricating oils. A typical single stage process is disclosed in US.Patent 2,960,458. Occasionally the two processes have been combined withthe hydrocgnation step being used to upgrade the oil produced byhydrocracking. Typical examples of this combination will be found inU.S. Patents 2,779,713; 2,787,582; and 2,917,448.

3,506,565 Patented Apr. 14, 1970 Until now, however, the existinghydrotreating processes have not been capable of producing high VI oilswith a wide range of viscosities. When hydrocrackers were operated toproduce high VI light neutral oils (as defined below), there would be avery poor yield of the heavy neutral oils. Conversely, whenhydrocracking under conditions to produce good yields of heavy neutraloils, the VIs of the light neutral oils would be seriously affected.

SUMMARY OF THE INVENTION We have now discovered a novel process for theproduction of high viscosity index lubricating oils with a wide range ofviscosities which comprises: hydrocracking in a first hydrocrackingzone, at a temperature of 700-850 F., to a conversion of at least 20percent to materials boiling below its initial boiling point, a firsthydrocarbon oil feed, boiling in the range of 800"-1,200 F. andcontaining less than 5 weight percent asphaltenes; separating from theeflluent of the first zone a plurality of hydrocarbon fractionsincluding at least one light oil fraction boiling in the range of700'900 F.; hydrocracking in a second hydrocracking zone, to aconversion of at least 20 percent to materials below the second feedinitial boiling range and at a temperature of 700850 F., the light oilfraction and a second hydrocarbon oil feed boiling in the range of7001,100 F., having an average boiling point no higher than the averageboiling point of the first oil feed, and containing less than 5 Weightpercent asphaltenes and finally recovering from the eflluents of bothzones a plurality of lubricating oils, including from the efi luent ofsaid first zone at least one 800+ neutral oil having a viscosity indexof at least and from the efliuent of said second zone at least one -150neutral oil having a viscosity index of at least 100. Preferably eachoil feed contains less than 1 weight percent asphaltenes, because oilswith high alphaltenes contents tend to foul the hydrcracking catalysts.The hydrocracked efiluents of each zone may be wholly or partiallydewaxed and/or stabilized to ultraviolet light.

DETAILED DESCRIPTION OF THE INVENTION In its broadest embodiment, theprocess of this invention comprises hydrocracking in a firsthydrocracking zone at a temperature of 700-850 -F., to a conversion ofat least 20 percent to materials boiling below its initial boilingpoint, a first hydrocarbon oil feed, boiling in the range of 8001,200 F.and containing less than 5 weight percent asphaltenes; separating fromthe efiiuent of said first zone a plurality of fractions, including atleast i one light oil fraction boiling in the range of 700900 F.;hydrocracking in a second zone, at a temperature of 700-850 F., to aconversion of at least 20 percent to materials boiling below the secondfeed initial boiling point, the light oil fraction and a secondhydrocarbon oil feed boiling in the range of 700-1,100 F., having anaverage boiling point no higher than the average boiling point of saidfirst oil feed, and containing less than 5 weight percent asphaltenes;and finally recovering from the efiluents of both zones a plurality oflubricating oils, including from the effiuent of said first Zone atleast one 800+ neutral oil having a viscosity index of at least 95 andfrom the efiluent of said second zone at least one 100-150 neutral oilhaving a viscosity index of at least 100. Preferred forms of the processof this invention will be described below.

The two hydrocracking zones are principal features of the process ofthis invention. They are conventional hydrocracking zones, comprisingcatalyst-containing vessels in which the lubricating oil stocks areconverted to the desired products in the presence of hydrogen and acatalyst. Suitable hydrocracking catalysts for use in the process ofthis invention are those solid contact materials having the propertiesof accelerating scission of carbon-carbon bonds and of acceleratinghydrogenation of cracked hydrocarbon fragments so produced. For purposesof the present invention in its preferred aspects, is is highlyadvantageous to employ a catalyst which maintains high activitythroughout continuous operation for periods of time of at least 600hours, and more preferably in the neighborhood of from two to severalthousand hours, without regeneration. These requirements are met by manyknown catalysts, which usually are composed of a refractory oxide incombination with an active hydrogenating metal component of Group VIIIof the Periodic Table and a hydrogenating metal component of Group VI ofthe Periodic Table. It is generally desirable to convert the metalcomponents to the sulfides to develop their maximum catalytic activityfor hydrocracking oils containing nitrogen compounds.

Particularly good refractory oxides are the high surface porous oxidecogels or coprecipitates of silica with alumina or magnesia, wherein thesilica and the alumina or magnesia are each present to the extent of atleast percent. Other high surface area cogels with materials such aszirconia, titania, or boria can also be used. The single ingredientsalumina, silica, or magnesia do not themselves appear to have sufiicientcracking activity to be considered within the preferred refractoryOxides. Preferred Group VIII components are the oxides and sulfides ofthe iron group and noble metals, cobalt, nickel, platinum, andpalladium, and especially nickel. Preferred Group VI components are theoxides and sulfides of molybdenum and tungsten. Thus examples ofhydrocracking catalysts which would be preferred for use in the processare the combinations nickel-tungsten-silicamagnesia,nickel-tungsten-silica-alumina, nickel-molybdenum-silica-alumina, andnickel-molybdenum-silica-magnesia. Such catalysts may vary greatly intheir activities for hydrogenation and for cracking and in their abilityto sustain high activity during long periods of use depending on theircompositions and methods of prepaation. Obviously, the best provencatalyst available is selected, taking into consideration all of theabove factors and also price.

Numerous schemes can be devised for bringing together the oils,hydrogen, and the catalyst at the temperature and pressure conditionsfor catalytic hydrocracking. Thus, the catalyst may be suspended in theoil as finely divided particles, or it may gravitate through the oil asrelatively large particles. The oil and hydrogen may be passed upwardsor downwards concurrently or countercurrently in one or more parallel orseries-connected reaction chambers. Probably the most suitablecommercial method for carrying out the process continuously, however,comprises preheating the oil and hydrogen under pressure and thenpassing them downward through one or more stationary beds of catalystparticles contained in a high pressure reactor. The amount of hydrogenpassed through the reactor is in substantial excess of the amountconsumed in hydrogenation reaction occurring therein, and the gas usedis sufficiently pure, so that the hydrogen partial pressure at all timesconstitutes the major portion of the total pressure. Hydrogenconsumption in each zone is in excess of 500 standard cubic feet perbarrel of fresh feed, and a particularly preferred range of hydrogenconsumption is 1200-3000 standard cubic feet of hydrogen per barrel offresh feed. If desired, excess hydrogen from the first zone may bepassed into the second zone.

The hydrocarbon oil feed to the first zone, referred to as the firstfeed, is a hydrocarbon oil boiling in the range of 800l,200 F. It may bea heavy straightrun gas oil, a deasphalted oil, or the like. It maypreviously have been desulfurized or denitrified. Preferred first feedsare those boiling at 900 F. or higher. The hydrocarbon oil feed to thesecond reaction zone, referred to as the second feed, is a hydrocarbonoil boiling in the range of 700l,l00 F. and is no heavier than the firststock (i.e., has an average boiling point no higher than the averageboiling point of the first stock). Preferably, the second feed issomewhat lighter than the first feed, for the former is primarilyintended to be a source of the lighter neutral oils, while the latter isprimarily intended to be a source of the heavy neutral oils. The secondfeed may also be a straight-run gas oil or any other hydrocarbon oilboiling within the proper range. Because of poisoning effect on thecatalysts caused by cracking of asphaltenes to coke, it is required thatthe stocks each contain less than 5 percent, by weight, of asphaltenes.Preferably, in order to minimize poisoning, the asphaltcne content isbelow 1 percent, by weight.

Reaction conditions in the first zone are temperatures within the rangeof 700-850 F., hydrogen pressures between 1,0005,000 p.s.i.g., andliquid hourly space velocities between 0.ll0.0. At these conditionsthere is at least 20 percent conversion of the feed material to productsboiling below the feed initial boiling point. Under these conditions avariety of reaction products will be formed as the high boiling firststock is cracked to lower boiling products. The efiluent of this zonewill contain, among other products, a light oil fraction boiling between700850 F. This product is separated from the reaction zone efiiuent andpassed to the second zone for further hydrocracking, this timesimultaneously with the second stock. Reaction conditions in the secondzone are within the same ranges as in the first zone; but, because thefeed to the second zone contains lighter materials, the precise reactionconditions are somewhat milder. It is preferred to obtain these milderconditions by holding temperature and pressure approximately by the samein both reaction zones, but permitting a higher liquid hourly spacevelocity in the second zone. Particularly preferred is a space velocity1.5-3.0 times greater than that in the first zone.

The efiiuents of the two hydrocracking zones contain a wide variety ofproducts. Some are light gases and other products boiling below thelubricating oil range, and these are separated and recovered as productsor passed on to further processing. The various lubricating oilfractions are separated according to their neutral oil ratings. Aneutral oil rating is simply the viscosity of a given oil fraction atF.; thus, a 100 neutral oil is an oil fraction which has a viscosity of100 S.U.S. at 100 F.

The advantages of the process over those of the prior art lie in theability of this process to produce a wide viscosity range of oils, allof which have high VIs. Consequently, it is required that included amongthe lubricating oils recovered from the effluents of the zones be atleast one oil having a neutral oil rating between 100 and 150 (i.e., a100-150 neutral oil) and a VI of at least 100., and at least one oilhaving a neutral oil rating of at least 800 (i.e., an 800+ neutral oil)and a VI of at least 95. In a typical operation of the process of thisinvention, a neutral oil, a 300 neutral oil, and an 800 neutral oilwould be separated and recovered. Other combinations are often used andcan be adjusted to meet the processors needs.

Occasionally the oils as produced, especially the heavier neutral oils,do not have sufficiently low pour points to meet a particularspecification. In this case, it is preferred to dewax that portion ofthe zone effluents, which is to be separated into the lubricating oils(as e.g., by distillation), prior to that separation. Dewaxing may be byconventional methods, such as solvent dewaxing. A preferred method isthe novel catalytic dewaxing process claimed in copending applicationSer. No. 704,556.

In the past it has been noticed that some oils produced by hydrocrackingshow a degree of instability in the presence of ultraviolet light Thisinstability is evidenced by the formation of a dark precipitate when theoil is exposed to natural or artificial ultraviolet light. The lightneutral oils tend to show a higher degree of instability (e.g., byforming a precipitate more rapidly) than do the heavier neutral oils.This instability can be overcome by conventional stabilizationprocesses, the most common of which is solvent extraction with a solventsuch as phenol or furfural.

The following example will illustrate the process of this invention. Inthe first reaction zone, a 9001,150 F. straight-run gas oil having agravity of 190 API, a sulfur content of 0.7 percent, and nitrogencontent of 0.22 percent was hydrocracked over a catalyst comprisingnickel and tungsten on an active cracking support. The reactiontemperature was 790 F., the hydrogen partial pressure was 2,200p.s.i.g., and the liquid hourly space velocity of the feed was 0.85.Hydrogen throughput was 8,000 s.c.f./bbl. of which 1,200 s.c.f./bbl. wasconsumed. The reaction products of the first Zone were a 50 percentyield of 750 F.-- hydrocarbons, a 9 percent yield of 750840 F. lightlubricating oil, a 9 percent yield of an 840910 F. heavy lubricatingoil, and a 32 percent yield of a 910 F.+ heavy oil. The products werenitrogenand sulfur-free, the nitrogen and sulfur having been convertedto ammonia and H s, respectively. On dewaxing, the 840-9l0 F. cutproduced a 300 neutral oil having a VI of 97 while the 910 F.+ cutproduced an 800 neutral oil having a VI of 98.

The light lubricating oil boiling between 750840 F. and having a VIbelow 90, was passed to a second reaction zone in which it was combinedas one part in ten with a straight-run gas oil to make a feed boiling inthe range of 670 F.-1,095 F. This feed had a gravity of 22.3 API, asulfur content of 0.4 percent, and a nitrogen content of 0.19 percent.This feed was hydrocracked over the same type of catalyst as that in thefirst reaction zone at a temperature of 790 F., a liquid hourly spacevelocity of 1.25, and a hydrogen partial pressure of 2,200 p.s.i.g. Thehydrogen throughput rate was 8,000 s.c.f./bbl. of which 1,000s.c.f./bbl. was consumed. The products of this second reaction zone werea 64 percent yield of 750 F.- hydrocarbons, a 19 percent yield of a 750-850 F. oil which, when dewaxed, produced a 130 neutral oil having a VIof 100, and a 17 percent yield of an 850 F.+ oil which, on dewaxing,produced a 300 neutral oil having a VI of 106.

The individual oil samples and VI measurements were made on samples ofthe separate eflluents. The eflluents of both reaction zones (except forthe test samples removed) were combined for dewaxing and stabilizing andthen were distilled into the respective cuts: a 750 F. light hydrocarboncut, the 130 neutral oil with a VI of 100, a combined 300 neutral oilhaving a VI of 103, and the 800 neutral oil with a VI of 98.

The example and data above are given for illustrative purposes and arenot meant to limit the scope of the process of this invention. Theinvention is to be limited only in accordance with the appended claims.

We claim:

1. A process for producing a lubricating oil stock comprised of highviscosity index fractions having a wide range of viscosities, whichcomprises contacting, in a first hydrocracking step, a first hydrocarbonoil feed having as asphaltene content below by weight and boiling in therange about 800 to 1200 F. and hydrogen with a solid hydrocrackingcatalyst under hydrocracking conditions to convert the feed to a producthaving a substantial proportion, not less than 20% by volume of thefeed, to products boiling below the initial boiling point of the feedand a substantial content of 800 neutral oil having a viscosity indexabove 95, separating from the product of the first hydrocracking step afraction boiling in the range about 700 to 900 F., contacting in asecond hydrocracking step a combined feed comprising said separatedfraction and a second hydrocarbon oil feed having an asphaltene contentbelow 5% by weight and boiling in the range about 700 to 1100 F. andhydrogen with a solid hydrocracking catalyst under hydrocrackingconditions to convert a substantial proportion at least 20% by volume ofsaid combined feed to products boiling below the initial boiling pointof the combined feed, the catalyst in both hydrocracking steps beingcomprised of a hydrogenation component and a refractory oxide crackingcomponent.

2. The process of claim 1, wherein the asphaltene content of each ofsaid hydrocarbon oil feeds is below 1% by weight.

3. The process of claim 1, wherein the average boiling point of thesecond hydrocarbon oil feed is below the average boiling point of thefirst hydrocarbon oil feed.

4. The process of claim 1, wherein the hydrocracking catalyst in bothhydrocracking steps is comprised of a Group VI metal or metal compoundand a Group VIII metal or metal compound supported on an acidic carrier,the temperature in both of said hydrocracking steps is maintained in therange 750 to 820 F., the pressure in both hydrocracking steps ismaintained in the range 1200 to 3000 p.s.i.g., the liquid hourly spacevelocity in both hydrocracking steps is in the range 0.3 to 5.0, and thehydrogen consumption in both hydrocracking steps is in excess of 500standard cubic feet per barrel of feed.

5. A process for producing a lubricating oil stock comprised of highviscosity index fractions having a wide range of viscosities, whichcomprises contacting, in a first hydrocracking step, a first hydrocarbonoil feed having an asphaltene content below 5% by weight and boiling inthe range about 800 to 1200 F. and hydrogen with a solid hydrocrackingcatalyst under hydrocracking conditions to convert the feed to a producthaving a substantial proportion, not less than 20% by volume of thefeed, to products boiling below the initial boiling point of the feedand a substantial content of 800 neutral oil having a viscosity indexabove 95, separating from the product of the first hydrocracking step afraction boiling in the range about 700 to 900 F., contacting in asecond hydrocracking step a combined feed comprising said separatedfraction and a second hydrocarbon oil feed having an asphaltene contentbelow 5% by weight and boiling in the range 700 to 1100 F. and hydrogenwith a solid hydrocracking catalyst under hydrocracking conditions toconvert a substantial proportion at least 20% by volume of said combinedfeed to products boiling below the initial 'boiling point of thecombined feed, the catalyst in both hydrocracking steps being comprisedby a hydrogenation component and a refractory oxide cracking component,dewaxing the remainder of the product of the first hydrocracking stepand the product of thesecond hydrocracking step and recovering from thedewaxed products a light lubricating oil fraction about -150 neutralhaving a viscosity index above 100 and a heavy lubricating oil fractionabout 800 neutral having a viscosity index above about 95.

References Cited UNITED STATES PATENTS 2,917,448 12/ 1959 Beuther et al.20857 3,436,334 4/1969 Orkin et al 20857 DELBERT E. GANTZ, PrimaryExaminer A. RIMENS, Assistant Examiner US. Cl. X.R.

